Hemolytic Disease of the Fetus and Newborn (HDFN)

Hemolytic disease of the fetus and newborn (HDFN), often called erythroblastosis fetalis, is a blood disorder that occurs when the blood types of a mother and baby are incompatible. For reference, “Hemolytic” means breaking down of the red blood cells and “Erythroblastosis” refers to the making of immature red blood cells.
This is a disease that often confuses many expectant parents and by better understanding the disease, many of the treatments required may be less stressful. With proper and timely treatment, the effects of the disease can often be minimized.

What is red cell alloimmunization, also known as Rh Disease, and how does one get it?

To understand red cell alloimmunization, one must first understand about the different blood group factors. These factors appear on the surface of the red blood cell in the form of antigens. The main blood group factor system is the commonly known ABO system. These are four basic blood types in this system: A, B, AB, and O. Rh (D) is another blood group antigen that is either present or absent on human red blood cells. When a patient is called Rh negative, she does NOT have the Rh(D) antigen present on her red blood cells, whereas if an individual is called Rh positive, the antigen is present. There are a variety of other red blood cells antigen systems found in humans. These include Kell, Duffy, Kidd, and MNS. In general, much like the Rh system, these antigens are either present and the individual is called positive for the antigen, or absent and the individual is called negative for the antigen.

When a woman becomes pregnant, genes (inherited traits) from her egg are combined with genes from her partner’s sperm. Together a unique embryo (future baby) is formed. This embryo carries with it genes from both the mother and the father. These genes include traits such as hair color, body build, ABO blood type, and Rh factor. Red cell alloimmunization, also known as Rh disease, occurs in response to an antibody (a protein substance that reacts to unrecognized proteins in the body) that is formed by the mother. These antibodies are usually formed in response to receiving blood during a blood transfusion that was different from your own, or more commonly during a miscarriage, abortion, or after the delivery of a child, when the baby’s blood mixes with your own.

If your blood is negative for a particular antigen and the baby’s blood cells carry the antigen, you may form antibodies against your baby’s red blood cells. During subsequent pregnancies, these antibodies cross the placenta and attach to the red blood cells of the baby. These antibodies can be measured in your bloodstream through a test called a titer or indirect Coombs test. If enough of these antibodies are present in your bloodstream (titer of 32 or more in most cases; titer of 8 for Kell disease), they may cause the baby’s red blood cells to break open, which may cause the baby to become anemic (have a low blood count) or become jaundiced (yellow). The disease process that occurs in the fetus or baby is known as hemolytic disease of the fetus/newborn. It is a direct result of the red cell alloimmunization in the mother. In severe cases the baby develops generalized edema (swelling all over his/her body), also known as hydrops fetalis. In the most severe cases, heart failure or even death in the womb may occur.

Many physicians affiliated with Children’s Memorial Hermann Hospital are faculty at McGovern Medical School at UTHealth. The affiliated physicians from McGovern Medical School consults with patients at UT Physicians clinic with all advanced treatments provided at Children’s Memorial Hermann Hospital.